Roofing waterproof engineering always is an important and challenging task needed to be improved. Building floor or cement floor inflicted water leakage mostly caused by cracks of floor, hence external water permeates through the cracks and flows indoors, and results in water leakage and efflorescence. On rooftop floor, cracks could be formed naturally, such as due to weathering for a long period of time, or drastic external climate changes, and cold and hot temperature differences that create chinks. Other external impacts such as earthquake and natural disasters also could produce cracks and chinks of varying sizes.
Due to different objectives, a wide variety of facilities or structures could be installed on building floors, such as solar panels and standpipes on the rooftop, huge commercial billboards and signboards on the building, etc. Installing those external facilities or structures often have to drilling bores on the floor, and fastening bolts or screws in the bores to mount base frames of the external facilities or structures thereon, then fastened with nuts. Drilling the bores through the floor or merely at a selected depth without running through the floor, and thrusting the screws in the bores tend to create small cracks and chinks and cause water leakage of the floor.
In the conventional techniques, after the bolt or screw has been disposed in the drilled hole, waterproof sealant is applied around the drilled hole to overcome water leakage problem. However, the waterproof sealant has limited durability, and often loses its efficacy due to degradation caused by sun shining. It also needs periodical maintenance. Moreover, adhesion between the waterproof sealant and floor often is not desirable. Water easily permeates through the interface between them and water leakage problem is not fully solved. Another approach is to install waterproof washers or O-ring on the nut or screw to prevent water from permeating through the gap formed between the bolt and bore after fastening the nut or screw. Reference can be found in U.S. Pat. No. 5,156,509 entitled “Waterproof screw fastener” and U.S. publication No. 2009/0104000 entitled “Waterproof structure for portion where members are tightened with screw”. But they all provide a limited waterproof scope without covering an extensive area surrounding the drilled bore.